Re: Fwd: iRiver Codec - RT encoding and Fixed point library

There may well be some sort of fixed point instructions in certain
versions of the coldfire. However, not on the CF5249 that H1xx/H3xx use,
(other than the more simple fractional mode of the EMAC unit, which we are
already using in all of our codecs).

If there is a fixed-point version of Shine MP3 encoder already optimised
for ARM then that is probably a good starting point. I'm not sure of the
merits of 'emulating' floating point using a fixed-point CPU, however (it
will either require major rewrites of the code or would just run
suboptimally - in either case, rewriting to use fixed-point data would
probably be a necessity)

d

> Hello,
>
> I follow the rockbox porting effort to iriver from the very beginning
> and I'm quite impressed by the work done so far.
>
> My freetime is limited and maybe I won't be able to write any line of
> C (but who knows), but I was curious about the "Real Time encoding"
> subject.
>
> There are comments in the wiki about ShineMP3 encoder and fixed point.
> Is there anybody here interested by the subject?
>
> Quote from the wiki:
> What about a fixed point library ? Can't we use a floating point
> algorithm with a fixed point library ? Furthermore, it seems that
> there is some sort of fixed point instructions in certain versions of
> the coldfire.
>
> http://www.mactech.com/articles/mactech/Vol.13/13.11/Fixed-PointMathSpeed/> http://www.freescale.com/files/32bit/doc/reports_presentations/V4PRES.html#mac>
> Does someone here know if we could use floating point code with a
> fixed point (mainly inlined) library ? Is lame too complicated for
> this use ? (maybe it is).
>
> Furthermore, such a library could be used by other modules of rockbox...
>
> What do you think about this ?
>
> Robin
>
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